This invention relates to sealant compositions. In another aspect, this invention relates to rubber-based sealants. In still another aspect, this invention relates to a rubbery polymer-based sealant composition containing a thixotropic system comprising a barium sulfate filler and a compound containing at least two acidic hydrogens that are attached to oxygen atoms. In still another aspect, this invention relates to a rubbery polymer sealant composition containing a thixotropic system comprising barium sulfate and a substituted phenol antioxidant or water. In yet another aspect, this invention relates to a sealant composition comprising a rubbery polymer ingredient that does not contain any oxygenated functional groups, a modifying resin compatible with the rubbery polymer, a plasticizer and a thixotropic system comprising barium sulfate and a substituted phenol antioxidant or water. In another aspect, this invention relates to a rubber-based sealant with improved sag resistance comprised of an elastomeric-type polymer, modifying resins, plasticizers, fillers, hydrocarbon solvents and a substituted phenol antioxidant.
Sealants are applied to exterior building joints to prevent the passage of outside environmental conditions such as wind, rain, dust, noise, etc. One of the basic requirements for such a building sealant is that the sealant does not sag, particularly in vertical joints, before the sealant has set. Setting is sometimes referred to as curing or solvent evaporation depending on the type of sealant employed. To promote non-sag properties, certain additives, sometimes referred to as thixotropic agents, are added to the sealant composition. Such additives can be materials like clays, mineral carbonates, carboxymethyl cellulose, fumed silica, and barium sulfate.
U.S. Pat. No. 3,798,129 discloses the use of fumed silica as a thixotropic agent. Although satisfactory in many cases, the material can sometimes contribute to cracks. Texture is also a very important property for a sealant as the cracking of a sealant tends to aid deterioration and undermine the basic function of the sealant. It is also expensive and, thus, can raise the overall cost of the composition. Also, because of the ultra fine particle size and low bulk density of fumed silica, special breathing masks are recommended during its use.
U.S. Pat. No. 3,627,707 discloses the use of two types of barium sulfate (precipitated and water-ground) to impart thixotropic properties to gasket-forming compositions. Barium sulfate, as is the case with fumed silica, does not always work well by itself and sometimes requires additional materials to enhance thixotropic properties. Fumed silica can employ water as a complexing agent, however, nothing is reported necessary to aid in the thixotropic properties of barium sulfate even though the material does not always work as well as desired. It would be of some technical importance, as well as some economic advantage, if an agent could be found that would improve the sag resistance of a sealant containing barium sulfate without hindering the texture. It would be especially advantageous if the agent could serve in two or more capacities in the sealant composition. For example, a material to enhance the thixotropic character of barium sulfate that could also be used as a filler, pigment, antioxidant or other such type sealant ingredient.
Accordingly, it is an object of this invention to provide a rubber-based sealant composition with improved sag resistance.
Another object of this invention is to provide a means of improving sag resistance in a sealant composition.
Another object of this invention is to provide a sealant composition having improved crack resistance as well as improved sag resistance.
Still another object of this invention is to provide a means for improving the overall performance properties of a sealant.
Other objects, aspects, and the several advantages of this invention will be apparent to those skilled in the art upon a study of this disclosure and the appended claims.